Infrared thermal imaging detectors are widely used for a variety of applications, such as to provide night vision, surveillance, and for search and rescue. Imaging devices to provide these applications are typically constructed of HgCdTe or InSb focal plane arrays. Such arrays have been difficult to manufacture, and are expensive. Quantum well infrared photodetectors (QWIPs) can detect mid and far infrared light, providing an output current as a result. However, such devices have not been able to be successfully used in efficient and inexpensive arrays to provide a practical imaging detector.
QWIP devices are described in U.S. Pat. No. 4,873,555, issued Oct. 10, 1989 to the University of Pittsburgh and in U.S. Pat. No. 4,894,526 issued Jan. 16, 1990 to American Telephone and Telegraph Company, AT&T Bell Laboratories. The latter patent describes an improved efficiency QWIP device which utilizes a series of quantum wells.